1. Field of the Invention
This invention relates generally to fluid control valves and more specifically to an improved cam sleeve operator for valves of the plug type in which a tapered plug is raised to unseat associated slips and then rotated to a valve open position for opening the valve and in which the opposite actions are carried out to close the valve. The improved cam sleeve of the present invention is designed to facilitate the aforementioned vertical and rotational movements in the proper sequence while substantially simplifying the mechanical operator assembly thereby substantially reducing the overall maintenance and cost of such valves.
2. Prior Art
Plug type valves are well known in the prior art particularly in the oil and gas industries where their positive sealing and superior flow characteristics are advantageous for controlling the flow of such fluids. Plug type valves are generally the type in which a valve body is provided with a pair of coaxial ports which are connected to incoming and outgoing fluid lines for the movement of fluid under pressure therethrough. Typically, a plug is adapted to selectively rotate within the main chamber of the valve to either provide a continuous channel between the incoming and outgoing coaxial ports when the valve is in the open position or to provide a fluid tight seal in one or both of the coaxial interconnecting ports when the valve is in the closed position.
A particularly advantageous plug type valve operating mechanism is disclosed in U.S. Pat. No. 3,492,880 to Pearson which is assigned to the assignee of the present invention and is incorporated herein by reference. That patent discloses the use of a valve control and actuating mechanism that permits rotation and axial linear motion of the valve plug in separate discrete movements in order to effect inward and outward movement of the sealing mechanism to assure a good seal in a closed valve and to further assure withdrawal of the seal from the valve ports without substantially reducing the life of the seals by preventing them from forcefully rubbing along the inside surface of the valve body.
One drawback of the otherwise advantageous valve control and actuating mechanism disclosed in the aforementioned U.S. Pat. No. 3,492,880, is the relative complexity of the operator mechanism disclosed for providing the requisite sequential vertical and rotatable motion of the plug. Such complexity renders the operating mechanism, as well as the entire valve, more expensive to produce and to purchase and also more difficult and costly to maintain over its operating life. The present invention provides improvements of the aforementioned operator mechanism for vertical and rotational motion of the plug portion of the valve in a simpler and thus advantageous and novel configuration that permits achievement of all the aforementioned advantageous functional operating characteristics of the previously disclosed plug valve control and actuating mechanism while reducing the overall complexity of the valve, by decreasing the wear and tear on the valve structure and by also reducing the cost of manufacture and maintenance thereof. Relevant cam sleeve valve operators are shown in U.S. Pat. No. 4,195,816 to Thompson, et al and in U.S. Pat. Nos. 2,501,150 and 2,580,212 both to Anderson.